Apertureless near-field optical microscopy: Differences between heterodyne interferometric and non-interferometric images

Abstract

We analyze simulations of the image generation process in apertureless Scanning Near-Field Optical Microscopy to study the differences between heterodyne interferometric and non-interferometric detection schemes implemented in experiments. Beyond the well-known possibilities of interferometry to enhance signals and extract optical phase information, we find that heterodyne interferometric detection may in fact lead to more robust and easier to interpret experimental results. Further, our results illustrate how simulations that do not include the use of interferometric detection in a given experiment can lead to significant disagreements with the measurements.

Subdiffraction light focusing using a cross sectional ridge waveguide nanoscale aperture

“…3(b), Using low harmonic detection, the background from the AFM cantilever and surrounding regions makes it difficult to observe the true near field signal at sufficiently high resolution and unwanted background fringes appear the image in Fig. 6(c), which are commonly seen in s-NSOM measurements [24,25]. Higher harmonic signals as seen in Fig.…”

Imaging the Optical near Field in Plasmonic Nanostructures

“…The advantages of this method compared to non-interferometric has been discussed in several articles. 76,77 In addition to field intensity, heterodyne detection enables phase-contrast images which bring a valuable set of informations ( Fig.2(D)). 60 Added to this configuration the use of a cross-polarization side illumination and detection enhance the signal-to-noise ratio.…”

“…The advantages of this method compared with a non-interferometric scheme have been discussed in several articles. 76,77 In addition to field intensity, heterodyne detection enables phase-contrast images, which bring a valuable set of data (Fig. 2D).…”

Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser

“…In addition, the signal phase cannot be uniquely determined from a single self-homodyne measurement. Therefore, many s-SNOM experiments are performed using interferometric homodyne or heterodyne configurations, in which the scattered light from the tip is interfered with a reference field of controlled/modulated phase in an interferometer [19,30,32]. The interferometric methods allow measurement of both the magnitude and phase of the near-field signal, and can enhance the SNR in the case of weak signals scattered from the tip.…”